Understanding Cancer Stage vs. Cancer Grade

Your report may carry both a stage and a grade, often within a few lines of each other, often both written as small numbers. They are not two versions of the same measurement. Stage answers how far has this cancer spread? Grade answers how abnormal do the cells look under the microscope? A cancer can be low stage and high grade, or higher stage and low grade, or any combination in between. Mixing the two up is one of the most common reasons people misread their own paperwork.

Staging describes the physical extent of the cancer in your body. The most widely used method is the TNM system.

• T describes the size of the primary tumor and how deeply it has grown into nearby tissue, from TX (cannot be measured) up to T4.
• N describes whether cancer has been found in nearby lymph nodes, from N0 (none found) up to N3.
• M describes distant spread: M0 means none has been found, M1 means cancer has been found in a distant part of the body.

Those letters are combined into an overall stage group, usually written in Roman numerals. Stage 0 means abnormal cells are present but have not grown into surrounding tissue. Stages I to III describe cancers that are progressively larger or more extensively involved with nearby nodes. Stage IV means cancer has been found at a distant site.

Stage also comes in two forms. Clinical stage, written with a lowercase c as in cT2N0, is the estimate made before surgery from examination, imaging and biopsy. Pathological stage, written with a lowercase p as in pT2N1, is assigned after tissue has been removed and examined. They do not always match.

Grade describes appearance, not location. A pathologist compares your cells with normal cells from the same tissue. Cells that still look organized and close to normal are called well differentiated. Cells that have lost that structure are called poorly differentiated or undifferentiated.

The general scale runs:

• GX — grade cannot be assessed
• G1 — well differentiated, low grade
• G2 — moderately differentiated, intermediate grade
• G3 — poorly differentiated, high grade
• G4 — undifferentiated, high grade

As the National Cancer Institute puts it, the more normal the cells look, the less aggressive the cancer tends to be and the more slowly it tends to grow and spread.

Many cancers use their own grading systems instead of this generic scale. Prostate cancer uses the Gleason score and Grade Groups. Breast cancer commonly uses the Nottingham grade. Brain tumors, kidney cancers and sarcomas each have their own conventions. A grade 3 in one cancer does not mean the same thing as a grade 3 in another.

Both are small numbers. Both sit near each other on the page. Neither is labeled in plain English. It is entirely possible to have a Stage I, Grade 3 cancer: small and confined, but built from aggressive-looking cells. It is equally possible to have a Stage III, Grade 1 cancer: more widely spread, but slow-growing in character. Neither combination is an error, and neither cancels the other out.

Stage tends to shape the overall structure of treatment — whether surgery alone may be enough, whether radiation to a region is needed, whether treatment that travels through the whole body is recommended. Grade tends to influence intensity and urgency, and it feeds into recurrence-risk calculators. In some cancers grade is now built into the stage itself: modern breast and prostate staging combine anatomy with grade and biomarker results rather than using anatomy alone.

Find the line that gives the stage and the line that gives the grade, and read them as two separate facts about two separate things. If only one appears, that is often normal. Grade is not reported for every cancer type, and a full pathological stage cannot exist until surgery has happened.

Neither number, on its own, tells you what will happen to you. Both are inputs. Your care team combines them with the cancer's subtype, its biomarkers, your general health and what matters to you.

• NCI: Cancer Staging
• NCI: Pathology Reports Fact Sheet
• American Cancer Society: Understanding Your Pathology Report